Method for transmitting or receiving a HARQ-ACK signal in wireless communication system, and device therefor

ABSTRACT

A method for transmitting a hybrid automatic repeat and request (HARQ) ACK/NACK signal by a reception side in a wireless communication system may further comprise the steps of: receiving a transmission block including a plurality of code blocks from a transmission side; decoding the received transmission block; and transmitting an ACK/NACK for the transmission block in units of code block groups, wherein the code.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2017/004169, filed on Apr. 19, 2017,which claims the benefit of U.S. Provisional Application No. 62/326,023,filed on Apr. 22, 2016, the contents of which are all herebyincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method of transmitting/receiving a HARQ ACK/NACKsignal in a wireless communication system and an apparatus therefor.

BACKGROUND ART

The present invention proposes new and various frame structures for a5^(th) generation (5G) communication system. In a next generation 5Gsystem, scenarios can be classified into Enhanced Mobile BroadBand(eMBB), Ultra-reliable Machine-Type Communications (uMTC), MassiveMachine-Type Communications (mMTC), and the like.

The eMBB corresponds to a next generation mobile communication scenariohaving such a characteristic as high spectrum efficiency, high userexperienced data rate, high peak data rate, and the like, the uMTCcorresponds to a next generation mobile communication scenario havingsuch a characteristic as ultra-reliable, ultra-low latency, ultra-highavailability, and the like (e.g., V2X, Emergency Service, RemoteControl), and the mMTC corresponds to a next generation mobilecommunication scenario having such a characteristic as low cost, lowenergy, short packet, and massive connectivity (e.g., IoT).

DISCLOSURE OF THE INVENTION Technical Tasks

A technical task of the present invention is to provide a method for areceiving side to transmit a HARQ (hybrid automatic repeat and request)ACK/NACK signal in a wireless communication system.

Another technical task of the present invention is to provide a methodfor a transmitting side to receive a HARQ (hybrid automatic repeat andrequest) ACK/NACK signal in a wireless communication system.

Another technical task of the present invention is to provide areceiving side device transmitting a HARQ (hybrid automatic repeat andrequest) ACK/NACK signal in a wireless communication system

The other technical task of the present invention is to provide atransmitting side device transmitting a HARQ (hybrid automatic repeatand request) ACK/NACK signal in a wireless communication system.

Technical tasks obtainable from the present invention are non-limitedthe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, accordingto one embodiment, a method for transmitting a HARQ (hybrid automaticrepeat and request) ACK/NACK signal by a receiving side in a wirelesscommunication system, includes the steps of receiving a transport blockincluding a plurality of code blocks from a transmitting side, decodingthe received transport block, and transmitting ACK/NACK for thetransport block in a unit of a code block group. In this case, the codeblock group can include at least one or more code blocks.

When the code block group includes a plurality of code blocks, an ACKsignal can be transmitted only when the plurality of the code blocks areall successfully decoded.

When the code block group includes a plurality of code blocks, an NACKsignal can be transmitted when it fails to decode any one of theplurality of the code blocks.

The method may further include if NACK for the code block group istransmitted, receiving downlink control information for retransmissionfrom the transmitting side. In this case, the downlink controlinformation may include a number of code block to be retransmitted, acode block index, or a code block group index. The method may furtherinclude the step of receiving downlink control information for initialtransmission of the transport block from the transmitting side. In thiscase, the downlink control information for the initial transmission mayinclude information on the transport block.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a different embodiment, amethod for receiving a HARQ (hybrid automatic repeat and request)ACK/NACK signal by a transmitting side in a wireless communicationsystem, includes the steps of transmitting a transport block including aplurality of code blocks to a receiving side and receiving ACK/NACK forthe transport block in a unit of a code block group. In this case, thecode block group can include at least one or more code blocks.

When the code block group includes a plurality of code blocks, an ACKsignal may be received from the receiving side only when the pluralityof the code blocks are all successfully decoded.

When the code block group includes a plurality of code blocks, an NACKsignal may be received from the receiving side when it fails to decodeany one of the plurality of the code blocks.

The method may further include, if NACK for the code block group isreceived, transmitting downlink control information for retransmissionto the receiving side. In this case, the downlink control informationmay include a number of code block to be retransmitted, a code blockindex, or a code block group index.

The method may further include the step of transmitting downlink controlinformation for initial transmission of the transport block. In thiscase, the downlink control information for the initial transmission mayinclude information on the transport block. To further achieve these andother advantages and in accordance with the purpose of the presentinvention, according to a further different embodiment, a receiving sideapparatus for transmitting a HARQ (hybrid automatic repeat and request)ACK/NACK signal in a wireless communication system includes a receiverconfigured to receive a transport block including a plurality of codeblocks from a transmitting side, a processor configured to decode thereceived transport block, and a transmitter configured to transmitACK/NACK for the transport block in a unit of a code block group. Inthis case, the code block group may include at least one or more codeblocks.

When the code block group includes a plurality of code blocks, thetransmitter may transmit an ACK signal only when the plurality of thecode blocks are all successfully decoded.

When the code block group includes a plurality of code blocks, thetransmitter may transmit an NACK signal if it fails to decode any one ofthe plurality of the code blocks.

The transmitter may transmit one ACK/NACK per to the code block group.The transmitter may transmit the ACK/NACK via PUSCH (physical uplinkshared channel).

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a further differentembodiment, a transmitting side apparatus for receiving a HARQ (hybridautomatic repeat and request) ACK/NACK signal in a wirelesscommunication system includes a transmitter configured to transmit atransport block including a plurality of code blocks to a receiving sideand a receiver configured to receive ACK/NACK for the transport block ina unit of a code block group. In this case, the code block group caninclude at least one or more code blocks.

When the code block group includes a plurality of code blocks, thereceiver may receive an ACK signal from the receiving side only when theplurality of the code blocks are all successfully decoded.

When the code block group includes a plurality of code blocks, thereceiver may receive an NACK signal from the receiving side when itfails to decode any one of the plurality of the code blocks.

The transmitter may transmit one ACK/NACK per the code block group.

The receiver may receive the ACK/NACK via PUSCH (physical uplink sharedchannel).

Advantageous Effects

According to one embodiment of the present invention, it is able tosolve a problem of retransmitting the entire transport blocksretransmitted by a transmitting side by transmitting ACK/NACK in a unitof a code block group including one or more code blocks, therebyenhancing overall performance of a system.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a block diagram for configurations of a base station 105 and auser equipment 110 in a wireless communication system 100;

FIG. 2 is a diagram for LTE/LTE-A frame structure;

FIG. 3 is a diagram for an example of a resource grid of a downlink slotof 3GPP LTE/LTE-A system as one example of a wireless communicationsystem;

FIG. 4 is a diagram for an example of a downlink subframe structure of3GPP LTE system as one example of a wireless communication system;

FIG. 5 is a diagram for an example of an uplink subframe structure of3GPP LTE system as one example of a wireless communication system;

FIG. 6 illustrates an example of CCs and CA in the LTE-A system, whichare used in embodiments of the present disclosure;

FIG. 7 is a diagram illustrating an example of configuring a servingcell according to cross-carrier scheduling;

FIG. 8 is a block diagram illustrating rate matching which is performedby separating an encoded code block (CB) into a systematic part and aparity part.

BEST MODE Mode for Invention

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. In the following detailed description of the inventionincludes details to help the full understanding of the presentinvention. Yet, it is apparent to those skilled in the art that thepresent invention can be implemented without these details. Forinstance, although the following descriptions are made in detail on theassumption that a mobile communication system includes 3GPP LTE system,the following descriptions are applicable to other random mobilecommunication systems in a manner of excluding unique features of the3GPP LTE.

Occasionally, to prevent the present invention from getting vaguer,structures and/or devices known to the public are skipped or can berepresented as block diagrams centering on the core functions of thestructures and/or devices. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Besides, in the following description, assume that a terminal is acommon name of such a mobile or fixed user stage device as a userequipment (UE), a mobile station (MS), an advanced mobile station (AMS)and the like. And, assume that a base station (BS) is a common name ofsuch a random node of a network stage communicating with a terminal as aNode B (NB), an eNode B (eNB), an access point (AP) and the like.Although the present specification is described based on IEEE 802.16msystem, contents of the present invention may be applicable to variouskinds of other communication systems.

In a mobile communication system, a user equipment is able to receiveinformation in downlink and is able to transmit information in uplink aswell. Information transmitted or received by the user equipment node mayinclude various kinds of data and control information. In accordancewith types and usages of the information transmitted or received by theuser equipment, various physical channels may exist.

The following descriptions are usable for various wireless accesssystems including CDMA (code division multiple access), FDMA (frequencydivision multiple access), TDMA (time division multiple access), OFDMA(orthogonal frequency division multiple access), SC-FDMA (single carrierfrequency division multiple access) and the like. CDMA can beimplemented by such a radio technology as UTRA (universal terrestrialradio access), CDMA 2000 and the like. TDMA can be implemented with sucha radio technology as GSM/GPRS/EDGE (Global System for Mobilecommunications)/General Packet Radio Service/Enhanced Data Rates for GSMEvolution). OFDMA can be implemented with such a radio technology asIEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, E-UTRA (EvolvedUTRA), etc. UTRA is a part of UMTS (Universal Mobile TelecommunicationsSystem). 3GPP (3rd Generation Partnership Project) LTE (long termevolution) is a part of E-UMTS (Evolved UMTS) that uses E-UTRA. The 3GPPLTE employs OFDMA in DL and SC-FDMA in UL. And, LTE-A (LTE-Advanced) isan evolved version of 3GPP LTE.

Moreover, in the following description, specific terminologies areprovided to help the understanding of the present invention. And, theuse of the specific terminology can be modified into another form withinthe scope of the technical idea of the present invention.

FIG. 1 is a block diagram for configurations of a base station 105 and auser equipment 110 in a wireless communication system 100.

Although one base station 105 and one user equipment 110 (D2D userequipment included) are shown in the drawing to schematically representa wireless communication system 100, the wireless communication system100 may include at least one base station and/or at least one userequipment.

Referring to FIG. 1, a base station 105 may include a transmitted (Tx)data processor 115, a symbol modulator 120, a transmitter 125, atransceiving antenna 130, a processor 180, a memory 185, a receiver 190,a symbol demodulator 195 and a received data processor 197. And, a userequipment 110 may include a transmitted (Tx) data processor 165, asymbol modulator 170, a transmitter 175, a transceiving antenna 135, aprocessor 155, a memory 160, a receiver 140, a symbol demodulator 155and a received data processor 150. Although the base station/userequipment 105/110 includes one antenna 130/135 in the drawing, each ofthe base station 105 and the user equipment 110 includes a plurality ofantennas. Therefore, each of the base station 105 and the user equipment110 of the present invention supports an MIMO (multiple input multipleoutput) system. And, the base station 105 according to the presentinvention may support both SU-MIMO (single user-MIMO) and MU-MIMO (multiuser-MIMO) systems.

In downlink, the transmitted data processor 115 receives traffic data,codes the received traffic data by formatting the received traffic data,interleaves the coded traffic data, modulates (or symbol maps) theinterleaved data, and then provides modulated symbols (data symbols).The symbol modulator 120 provides a stream of symbols by receiving andprocessing the data symbols and pilot symbols.

The symbol modulator 120 multiplexes the data and pilot symbols togetherand then transmits the multiplexed symbols to the transmitter 125. Indoing so, each of the transmitted symbols may include the data symbol,the pilot symbol or a signal value of zero. In each symbol duration,pilot symbols may be contiguously transmitted. In doing so, the pilotsymbols may include symbols of frequency division multiplexing (FDM),orthogonal frequency division multiplexing (OFDM), or code divisionmultiplexing (CDM).

The transmitter 125 receives the stream of the symbols, converts thereceived stream to at least one or more analog signals, additionallyadjusts the analog signals (e.g., amplification, filtering, frequencyupconverting), and then generates a downlink signal suitable for atransmission on a radio channel. Subsequently, the downlink signal istransmitted to the user equipment via the antenna 130.

In the configuration of the user equipment 110, the receiving antenna135 receives the downlink signal from the base station and then providesthe received signal to the receiver 140. The receiver 140 adjusts thereceived signal (e.g., filtering, amplification and frequencydownconverting), digitizes the adjusted signal, and then obtainssamples. The symbol demodulator 145 demodulates the received pilotsymbols and then provides them to the processor 155 for channelestimation.

The symbol demodulator 145 receives a frequency response estimated valuefor downlink from the processor 155, performs data demodulation on thereceived data symbols, obtains data symbol estimated values (i.e.,estimated values of the transmitted data symbols), and then provides thedata symbols estimated values to the received (Rx) data processor 150.The received data processor 150 reconstructs the transmitted trafficdata by performing demodulation (i.e., symbol demapping, deinterleavingand decoding) on the data symbol estimated values.

The processing by the symbol demodulator 145 and the processing by thereceived data processor 150 are complementary to the processing by thesymbol modulator 120 and the processing by the transmitted dataprocessor 115 in the base station 105, respectively.

In the user equipment 110 in uplink, the transmitted data processor 165processes the traffic data and then provides data symbols. The symbolmodulator 170 receives the data symbols, multiplexes the received datasymbols, performs modulation on the multiplexed symbols, and thenprovides a stream of the symbols to the transmitter 175. The transmitter175 receives the stream of the symbols, processes the received stream,and generates an uplink signal. This uplink signal is then transmittedto the base station 105 via the antenna 135.

In the base station 105, the uplink signal is received from the userequipment 110 via the antenna 130. The receiver 190 processes thereceived uplink signal and then obtains samples. Subsequently, thesymbol demodulator 195 processes the samples and then provides pilotsymbols received in uplink and a data symbol estimated value. Thereceived data processor 197 processes the data symbol estimated valueand then reconstructs the traffic data transmitted from the userequipment 110.

The processor 155/180 of the user equipment/base station 110/105 directsoperations (e.g., control, adjustment, management, etc.) of the userequipment/base station 110/105. The processor 155/180 may be connectedto the memory unit 160/185 configured to store program codes and data.The memory 160/185 is connected to the processor 155/180 to storeoperating systems, applications and general files.

The processor 155/180 may be called one of a controller, amicrocontroller, a microprocessor, a microcomputer and the like. And,the processor 155/180 may be implemented using hardware, firmware,software and/or any combinations thereof. In the implementation byhardware, the processor 155/180 may be provided with such a deviceconfigured to implement the present invention as ASICs (applicationspecific integrated circuits), DSPs (digital signal processors), DSPDs(digital signal processing devices), PLDs (programmable logic devices),FPGAs (field programmable gate arrays), and the like.

Meanwhile, in case of implementing the embodiments of the presentinvention using firmware or software, the firmware or software may beconfigured to include modules, procedures, and/or functions forperforming the above-explained functions or operations of the presentinvention. And, the firmware or software configured to implement thepresent invention is loaded in the processor 155/180 or saved in thememory 160/185 to be driven by the processor 155/180.

Layers of a radio protocol between a user equipment/base station and awireless communication system (network) may be classified into 1st layerL1, 2nd layer L2 and 3rd layer L3 based on 3 lower layers of OSI (opensystem interconnection) model well known to communication systems. Aphysical layer belongs to the 1st layer and provides an informationtransfer service via a physical channel. RRC (radio resource control)layer belongs to the 3rd layer and provides control radio resourcedbetween UE and network. A user equipment and a base station may be ableto exchange RRC messages with each other through a wirelesscommunication network and RRC layers.

In the present specification, although the processor 155/180 of the userequipment/base station performs an operation of processing signals anddata except a function for the user equipment/base station 110/105 toreceive or transmit a signal, for clarity, the processors 155 and 180will not be mentioned in the following description specifically. In thefollowing description, the processor 155/180 can be regarded asperforming a series of operations such as a data processing and the likeexcept a function of receiving or transmitting a signal without beingspecially mentioned.

FIG. 2 is a diagram for LTE/LTE-A frame structure.

Referring to FIG. 2, a frame corresponds to 10 ms and includes 10 1-mssubframes. A time for transmitting one subframe is defined as atransmission time interval (TTI). For example, one subframe includes 20.5-ms slots. One slot includes 7 (or 6) orthogonal frequency divisionmultiplexing (OFDM) symbols. Since the 3GPP LTE uses the OFDMA in thedownlink, the OFDM symbol is for representing one symbol period. TheOFDM symbol may also be referred to as an SC-FDMA symbol or a symbolperiod. A resource block (RB) is a resource allocation unit, andincludes a plurality of contiguous subcarriers in one slot. Thestructure of the radio frame shown in FIG. 2 is shown for exemplarypurposes only. Thus, the number of subframes included in the radio frameor the number of slots included in the subframe or the number of OFDMsymbols included in the slot may be modified in various manners.

One RB (resource block) is defined by 12 subcarriers of an interval of15 kHz and 7 OFDM symbols. A base station transmits a primarysynchronization signal (PSS) and a secondary synchronization signal(SSS) for synchronization and a physical broadcast channel (PBCH) forsystem information on a center frequency (6 RBs). In this case, astructure of the radio frame, a signal, and a channel may vary accordingto a normal/extended CP (cyclic prefix), TDD (time division duplex)/FDD(frequency division duplex).

FIG. 3 is a diagram for an example of a resource grid of a downlink slotof 3GPP LTE/LTE-A system as one example of a wireless communicationsystem.

Referring to FIG. 3, a downlink slot includes a plurality of OFDMsymbols in time domain. It is described herein that one downlink slotincludes 7 (or 6) OFDM symbols, and one resource block (RB) includes 12subcarriers in frequency domain. Each element on the resource grid isreferred to as a resource element (RE). One RB includes 12×7(6) REs. Thenumber N of RBs included in the downlink slot depends on a downlinktransmit bandwidth. The structure of an uplink slot may be same as thatof the downlink slot. In this case, OFDM symbol is replaced with SC-FDMAsymbol.

FIG. 4 is a diagram for an example of a downlink subframe structure of3GPP LTE/LTE-A system as one example of a wireless communication system.

Referring to FIG. 4, a maximum of three (or four) OFDM symbols locatedin a front portion of a first slot within a subframe correspond to acontrol region to be assigned with a control channel. The remaining OFDMsymbols correspond to a data region to be assigned with a physicaldownlink shared chancel (PDSCH). Examples of downlink control channelsused in the LTE includes a physical control format indicator channel(PCFICH), a physical downlink control channel (PDCCH), a physical hybridARQ indicator channel (PHICH), etc. The PCFICH is transmitted at a firstOFDM symbol of a subframe and carries information regarding the numberof OFDM symbols used for transmission of control channels within thesubframe. The PHICH is a response of uplink transmission and carries anHARQ acknowledgment (ACK)/not-acknowledgment (NACK) signal.

Control information transmitted through the PDCCH is referred to asdownlink control information (DCI). A DCI format 0 is defined for UL andDCI formats 1, 1A, 1B, 1C, 1D, 2, 2A, 3, 3A, etc. are defined for DL.The DCI format selectively includes information such as a hopping flag,RB allocation, MCS (modulation coding scheme), an RV (redundancyversion), an NDI (new data indicator), TPC (transmit power control), acyclic shift DMRS (demodulation reference signal), CQI (channel qualityinformation) request, HARQ process number, a TPMI (transmitted precodingmatrix indicator), PMI (precoding matrix indicator) confirmation, andthe like according to a usage.

The PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, a resource allocation of anupper-layer control message such as a random access response transmittedon the PDSCH, a set of Tx power control commands on individual UEswithin an arbitrary UE group, a Tx power control command, activation ofa voice over IP (VoIP), etc. A plurality of PDCCHs can be transmittedwithin a control region. The UE can monitor the plurality of PDCCHs. ThePDCCH is transmitted on an aggregation of one or several consecutivecontrol channel elements (CCEs). The CCE is a logical allocation unitused to provide the PDCCH with a coding rate based on a state of a radiochannel The CCE corresponds to a plurality of resource element groups(REGs). A format of the PDCCH and the number of bits of the availablePDCCH are determined according to a correlation between the number ofCCEs and the coding rate provided by the CCEs. The base stationdetermines a PDCCH format according to a DCI to be transmitted to theUE, and attaches a cyclic redundancy check (CRC) to control information.The CRC is masked with a unique identifier (referred to as a radionetwork temporary identifier (RNTI)) according to an owner or usage ofthe PDCCH. If the PDCCH is for a specific UE, a unique identifier (e.g.,cell-RNTI (C-RNTI)) of the UE may be masked to the CRC. Alternatively,if the PDCCH is for a paging message, a paging indicator identifier(e.g., paging-RNTI (P-RNTI)) may be masked to the CRC. If the PDCCH isfor system information (more specifically, a system information block(SIB)), a system information identifier and a system information RNTI(SI-RNTI) may be masked to the CRC. To indicate a random accessresponse, a random access-RNTI (RA-RNTI) may be masked to the CRC.

FIG. 5 is a diagram for an example of an uplink subframe structure of3GPP LTE/LTE-A system as one example of a wireless communication system.

Referring to FIG. 5, an uplink subframe includes a plurality of (e.g. 2)slots. A slot may include different numbers of SC-FDMA symbols accordingto CP lengths. The uplink subframe is divided into a control region anda data region in the frequency domain. The data region is allocated witha PUSCH and used to carry a data signal such as audio data. The controlregion is allocated a PUCCH and used to carry uplink control information(UCI). The PUCCH includes an RB pair located at both ends of the dataregion in the frequency domain and hopped in a slot boundary.

The PUCCH can be used to transmit the following control information.

-   -   Scheduling Request (SR): This is information used to request a        UL-SCH resource and is transmitted using On-Off Keying (OOK)        scheme.    -   HARQ-ACK: This is a response to a downlink data packet (e.g.        codeword) on a PDSCH and indicates whether the downlink data        packet has been successfully received. A 1-bit ACK/NACK is        transmitted as a response to a single downlink codeword and a        2-bit ACK/NACK is transmitted as a response to two downlink        codewords.    -   Channel Quality Information (CQI): This is feedback information        about a downlink channel MIMO (Multiple Input Multiple        Output)-related feedback information includes a rank indicator        (RI), a precoding matrix indicator (PMI), and a precoding type        indicator (PTI). 20 bits per subframe are used.

The quantity of control information (UCI) that a UE can transmit througha subframe depends on the number of SC-FDMA symbols available forcontrol information transmission. The SC-FDMA symbols available forcontrol information transmission correspond to SC-FDMA symbols otherthan SC-FDMA symbols of the subframe, which are used for referencesignal transmission. In the case of a subframe in which a SoundingReference Signal (SRS) is configured, the last SC-FDMA symbol of thesubframe is excluded from the SC-FDMA symbols available for controlinformation transmission. A reference signal is used to detect coherenceof the PUCCH. The PUCCH supports 7 formats according to informationtransmitted thereon.

PDCCH (Physical Downlink Control Channel) Transmission

PDCCH corresponds to a downlink control channel. The PDCCH is configuredto transmit control information for transmitting PDSCH/PUSCH for aspecific UE and transmit a power control command for a plurality of UEs.The PDCCH occupies maximum 4 OFDM symbols in time domain and indicatesthe number of OFDM symbols assigned to the PDCCH using PCFICH.Meanwhile, the PDCCH is transmitted over the whole band in frequencydomain and uses QPSK for modulation. A resource used for transmittingthe PDCCH is referred to as a CCE (control channel element). Since a CCEincludes 36 resource elements, it may be able to transmit 72 bits via asingle CCE. The amount of control information transmitted on the PDCCHmay vary depending on a transmission mode. Control information accordingto a transmission mode is regulated by a DCI format. A UE determineswhether or not PDSCH/PUSCH is transmitted according to a PDCCH decodingresult. In this case, PDCCH scrambling is performed using UE IDinformation (C-RNTI) of a corresponding UE. In particular, if a UEdetects a DCI format, which is transmitted in a manner of beingscrambled by a UE ID of the UE, the UE transmits PDSCH or receives PUSCHaccording to PDCCH control information. In general, one subframeincludes a plurality of PDCCHs capable of being transmitted. Hence, itis necessary for a UE to check whether or not there is controlinformation transmitted to the UE by performing decoding on a pluralityof the PDCCHs. However, if the UE performs decoding on all of aplurality of the PDCCHs, complexity is considerably increased. Hence, itis necessary to set a limit on the number of performing decoding. Whencontrol information is transmitted via PDCCH, the control informationcan be transmitted in a manner of concatenating one or a plurality ofCCEs with each other. This is referred to as CCE aggregation. Currently,a CCE aggregation level is permitted by 1, 2, 4 and 8. If the CCEaggregation level corresponds to 4, it indicates that controlinformation of a corresponding UE is transmitted in a manner ofconcatenating 4 CCEs with each other. A UE sets limit on the decodingnumber according to each aggregation level. Table 1 in the followingshows the decoding number according to an aggregation level.

TABLE 1 Search space S_(k) ^((L)) Number of PDCCH Type Aggregation levelL Size [in CCEs] candidates M^((L)) UE-specific 1 6 6 2 12 6 4 8 2 8 162 Common 4 16 4 8 16 2

Referring to Table 1, in case of a common type, a UE performs decodingon PDCCHs, which are transmitted by an aggregation level 4 and 8, 4times and 2 times, respectively, to determine whether or not controlinformation is transmitted. A specific CCE constructing PDCCHcorresponds to a region commonly known to all UEs. In case of aUE-specific type, unlike the common type, a UE performs decoding onPDCCHs, which are transmitted by an aggregation level 1, 2, 4, and 8, 6,6, 2 and 2 times, respectively, to determine whether or not controlinformation is transmitted. In this case, a CCE is differentlyconfigured according to a UE. This can be represented as equation 1 inthe following.Y _(k)=(A·Y _(k−1))mod D  [Equation 1]

In this case, Y⁻¹=n_(RNTI)≠0, A=39827, D=65537 and k=└n_(s)/2┘. n_(s)corresponds to a slot number in a radio frame.

FIG. 6 illustrates an example of CCs and CA in the LTE-A system, whichare used in embodiments of the present disclosure.

FIG. 6(a) illustrates a single carrier structure in the LTE system.There are a DL CC and a UL CC and one CC may have a frequency range of20 MHz.

FIG. 6(b) illustrates a CA structure in the LTE-A system. In theillustrated case of FIG. 6(b), three CCs each having 20 MHz areaggregated. While three DL CCs and three UL CCs are configured, thenumbers of DL CCs and UL CCs are not limited. In CA, a UE may monitorthree CCs simultaneously, receive a DL signal/DL data in the three CCs,and transmit a UL signal/UL data in the three CCs.

If a specific cell manages N DL CCs, the network may allocate M (M≤N) DLCCs to a UE. The UE may monitor only the M DL CCs and receive a DLsignal in the M DL CCs. The network may prioritize L (L≤M≤N) DL CCs andallocate a main DL CC to the UE. In this case, the UE should monitor theL DL CCs. The same thing may apply to UL transmission.

The linkage between the carrier frequencies of DL resources (or DL CCs)and the carrier frequencies of UL resources (or UL CCs) may be indicatedby a higher layer message such as an RRC message or by systeminformation. For example, a set of DL resources and UL resources may beconfigured based on linkage indicated by System Information Block Type 2(SIB2). Specifically, DL-UL linkage may refer to a mapping relationshipbetween a DL CC carrying a PDCCH with a UL grant and a UL CC using theUL grant, or a mapping relationship between a DL CC (or a UL CC)carrying HARQ data and a UL CC (or a DL CC) carrying an HARQ ACK/NACKsignal.

Cross Carrier Scheduling

Two scheduling schemes, self-scheduling and cross carrier scheduling aredefined for a CA system, from the perspective of carriers or servingcells. Cross carrier scheduling may be called cross CC scheduling orcross cell scheduling.

In self-scheduling, a PDCCH (carrying a DL grant) and a PDSCH aretransmitted in the same DL CC or a PUSCH is transmitted in a UL CClinked to a DL CC in which a PDCCH (carrying a UL grant) is received.

In cross carrier scheduling, a PDCCH (carrying a DL grant) and a PDSCHare transmitted in different DL CCs or a PUSCH is transmitted in a UL CCother than a UL CC linked to a DL CC in which a PDCCH (carrying a ULgrant) is received.

Cross carrier scheduling may be activated or deactivated UE-specificallyand indicated to each UE semi-statically by higher layer signaling (e.g.RRC signaling).

If cross carrier scheduling is activated, a Carrier Indicator Field(CIF) is required in a PDCCH to indicate a DL/UL CC in which aPDSCH/PUSCH indicated by the PDCCH is to be transmitted. For example,the PDCCH may allocate PDSCH resources or PUSCH resources to one of aplurality of CCs by the CIE That is, when a PDCCH of a DL CC allocatesPDSCH or PUSCH resources to one of aggregated DL/UL CCs, a CIF is set inthe PDCCH. In this case, the DCI formats of LTE Release-8 may beextended according to the CIF. The CIF may be fixed to three bits andthe position of the CIF may be fixed irrespective of a DCI format size.In addition, the LTE Release-8 PDCCH structure (the same coding andresource mapping based on the same CCEs) may be reused.

On the other hand, if a PDCCH transmitted in a DL CC allocates PDSCHresources of the same DL CC or allocates PUSCH resources in a single ULCC linked to the DL CC, a CIF is not set in the PDCCH. In this case, theLTE Release-8 PDCCH structure (the same coding and resource mappingbased on the same CCEs) may be used.

If cross carrier scheduling is available, a UE needs to monitor aplurality of PDCCHs for DCI in the control region of a monitoring CCaccording to the transmission mode and/or bandwidth of each CC.Accordingly, an appropriate SS configuration and PDCCH monitoring areneeded for the purpose.

In the CA system, a UE DL CC set is a set of DL CCs scheduled for a UEto receive a PDSCH, and a UE UL CC set is a set of UL CCs scheduled fora UE to transmit a PUSCH. A PDCCH monitoring set is a set of one or moreDL CCs in which a PDCCH is monitored. The PDCCH monitoring set may beidentical to the UE DL CC set or may be a subset of the UE DL CC set.The PDCCH monitoring set may include at least one of the DL CCs of theUE DL CC set. Or the PDCCH monitoring set may be defined irrespective ofthe UE DL CC set. DL CCs included in the PDCCH monitoring set may beconfigured to always enable self-scheduling for UL CCs linked to the DLCCs. The UE DL CC set, the UE UL CC set, and the PDCCH monitoring setmay be configured UE-specifically, UE group-specifically, orcell-specifically.

If cross carrier scheduling is deactivated, this implies that the PDCCHmonitoring set is always identical to the UE DL CC set. In this case,there is no need for signaling the PDCCH monitoring set. However, ifcross carrier scheduling is activated, the PDCCH monitoring set may bedefined within the UE DL CC set. That is, the eNB transmits a PDCCH onlyin the PDCCH monitoring set to schedule a PDSCH or PUSCH for the UE.

FIG. 7 is a diagram illustrating an example of configuring a servingcell according to cross-carrier scheduling.

Referring to FIG. 7, a base station and/or UEs for use in a radio accesssystem supporting carrier aggregation (CA) may include one or moreserving cells. In FIG. 7, the base station can support a total of fourserving cells (cells A, B, C and D). It is assumed that UE A may includeCells (A, B, C), UE B may include Cells (B, C, D), and UE C may includeCell B. In this case, at least one of cells of each UE may be composedof P Cell. In this case, P Cell is always activated, and SCell may beactivated or deactivated by the base station and/or UE.

The cells shown in FIG. 7 may be configured per UE. The above-mentionedcells selected from among cells of the base station, cell addition maybe applied to carrier aggregation (CA) on the basis of a measurementreport message received from the UE. The configured cell may reserveresources for ACK/NACK message transmission in association with PDSCHsignal transmission. The activated cell is configured to actuallytransmit a PDSCH signal and/or a PUSCH signal from among the configuredcells, and is configured to transmit CSI reporting and SoundingReference Signal (SRS) transmission. The deactivated cell is configurednot to transmit/receive PDSCH/PUSCH signals by a base station command ora timer operation, and CRS reporting and SRS transmission areinterrupted.

Physical Resource Block (PRB) Bundling

In case of a UE supporting a transmission mode 9, the UE can configurePMI/RI feedback via higher layer. The transmission mode 9 UE to whichthe PMI/RI feedback is set may make an assumption on granularity of aphysical resource block that applies the same precoding to PDSCH and aDM RS. In particular, the UE performs channel estimation under theassumption that the same precoding is applied to a precoding resourceblock group (PRG) according to a system bandwidth to enhance channelestimation capability. Table 2 in the following shows values of a PRGsize according to a system bandwidth.

TABLE 2 System bandwidth (N_(RB) ^(DL)) PRG size (PRBs) <=10 1 11~26 227~63 3 64~110 2

Channel Coding

FIG. 8 is a block diagram illustrating rate matching which is performedby separating an encoded code block (CB) into a systematic part and aparity part.

In a general communication system, in order to make a receiving endcorrect an error occurred at a channel, a transmitting end performscoding on information transmitted by the transmitting end using an errorcorrection code and transmits the information. Having received theinformation, the receiving end performs demodulation on a receptionsignal, performs a decoding procedure on the error correction code, andrestores the information. An error of the reception signal caused by achannel can be corrected by the decoding procedure. The error correctioncode may include various types. In the present invention, a turbo codeis explained as an example of the error correction code. The turbo codeconsists of a recursive systematic convolution encoder and aninterleaver. When the turbo code is actually implemented, an interleavermay exist to easily perform parallel decoding. QPP (quadratic polynomialpermutation) is a sort of the interleaver. It is known as the QPPinterleaver maintains good performance on a specific data block sizeonly. It is known as the performance of the turbo code is getting betteras a size of a data block is getting bigger. In an actual communicationsystem, if a data block has a size equal to or greater than a prescribedsize, the data block is divided into a plurality of small data blocks toeasily perform encoding. A divided small data block is referred to as acode block. In general, code blocks have the same size. Yet, due to asize restriction of the QPP interleaver, one of a plurality of codeblocks may have a different size. The error correction encodingprocedure is performed in a unit of a determined interleaver size codeblock and interleaving is performed to reduce an impact of a bursterror, which occurs when transmission is performed via a radio channel.The code block is transmitted in a manner of being mapped to an actualradio resource. Since the amount of radio resources used for performingactual transmission is constant, it is necessary to perform ratematching on the encoded code block to match with the amount of radioresource. In general, rate matching includes puncturing and repetition.The rate matching can be performed in such a unit of an encoded codeblock as WCDMA of 3GPP. As a different method, it may be able toseparately perform the rate matching in a manner of dividing the encodedcode block into a systematic part and a parity part.

In this case, a CRC for detecting an error is attached to a data blocktransmitted by higher layer. For clarity of implementation, a CRC isattached to a segmented code block as well. It is necessary to definevarious data block sizes according to a service type of higher layer.Yet, since it is necessary to signal the various data block sizes to areceiving end, quantization is required. When the quantization isperformed, in order to match a size of a source data block transmittedby higher later with a size of a data block of a physical layer, a dummybit is attached. When the quantization is performed, it is preferable tominimize the amount of attached dummy bits. A data block size,modulation and coding rate, and the number of allocated resources becomefunctional relation with each other. In particular, one parameter isdetermined by values of other two parameters. Hence, in case ofsignaling parameters, it may signal two parameters only. In thefollowing, for clarity, assume that modulation and coding rate and thenumber of allocated resources are used to inform a receiving end of adata block size. In this case, a pilot signal or a reference signal forchannel estimation, a resource for transmitting control information, andthe like may influence on the number of allocated resources according toan antenna configuration. A factor influencing on the number ofallocated resources may change at every transmission instant.

MCS (Modulation and Coding Scheme) Signaling

A base station uses a DL control channel (e.g., PDCCH/EPDCCH (enhancedPDCCH) to deliver a data block size to a receiving side (e.g., UE). Thebase station can transmit information on the data block size to thereceiving side on PDSCH by combining MCS corresponding to information ona modulation and coding rate with resource allocation information. TheMCS is configured by 5 bits and a resource can be allocated using 1 RBto 110 RBs. In particular, in case of non-MIMO, it may be able to signala data block size (overlapped size is permitted) as much as 32*110.However, since 3 states of the MCS field, which is transmitted by 5bits, are used for indicating the change of a modulation scheme at thetime of retransmission, it may signal a data block size (overlapped sizeis permitted) as much as 29*110. QPSK, 16 QAM, and 64 QAM are supportedas modulation schemes. When a modulation scheme is changed at aswitching point, if the same resource is allocated, the same data blocksize is indicated to efficiently operate in various channelenvironments. In order to indicate an actual data block size inconsideration of the abovementioned contents, MCS-related information(e.g., IMCS) transmitted via a DL control channel is mapped to adifferent variable. Table 3 in the following illustrates a relationbetween IMCS and ITBS.

TABLE 3 MCS Index Modulation Order TBS Index I_(MCS) Q_(m) I_(TBS) 0 2 01 2 1 2 2 2 3 2 3 4 2 4 5 2 5 6 2 6 7 2 7 8 2 8 9 2 9 10 4 9 11 4 10 124 11 13 4 12 14 4 13 15 4 14 16 4 15 17 6 15 18 6 16 19 6 17 20 6 18 216 19 22 6 20 23 6 21 24 6 22 25 6 23 26 6 24 27 6 25 28 6 26 29 2reserved 30 4 31 6

Downlink Transmission Mode and DCI Format

A bit configuration of control data transmitted via a DL control channelvaries according to a DL transmission mode. This is referred to as a DLcontrol information (DCI) format. A region in which the DL controlchannel is transmitted is divided into a common search space and aUE-specific search space. A control channel transmitted via the commonsearch space is transmitted in a manner of being scrambled by an ID suchas SI-RNTI/P-RNTI/RA-RNTI and uses a specific DCI format. Tables 4, 5,6, 7, 8, and 9 described in the following illustrate a DCI format, asearch space, and a transmission scheme when SI-RNTI, P-RNTI, RA-RNTI,C-RNTI, SPS C-RNTI, and temporary C-RNTI are used, respectively.

TABLE 4 DCI Control channel Transmission scheme of PDSCH format SearchSpace corresponding to PDCCH DCI Common If the number of PBCH antennaports is one, format Single-antenna port, port 1C 0 is used, otherwiseTransmit diversity. DCI Common If the number of PBCH antenna ports isone, format Single-antenna port, port 1A 0 is used, otherwise Transmitdiversity

TABLE 5 Transmission Control channel Search Transmission scheme of PDSCHmode DCI format Space corresponding to PDCCH Mode 1 DCI format 1A Commonand Single-antenna port, port 0 UE specific by C-RNTI DCI format 1 UEspecific by C-RNTI Single-antenna port, port 0 Mode 2 DCI format 1ACommon and Transmit diversity UE specific by C-RNTI DCI format 1 UEspecific by C-RNTI Transmit diversity Mode 3 DCI format 1A Common andTransmit diversity UE specific by C-RNTI DCI format 2A UE specific byC-RNTI Large delay CDD or Transmit diversity Mode 4 DCI format 1A Commonand Transmit diversity UE specific by C-RNTI DCI format 2 UE specific byC-RNTI Closed-loop spatial multiplexing or Transmit diversity Mode 5 DCIformat 1A Common and Transmit diversity UE specific by C-RNTI DCI format1D UE specific by C-RNTI Multi-user MIMO Mode 6 DCI format 1A Common andTransmit diversity UE specific by C-RNTI DCI format 1B UE specific byC-RNTI Closed-loop spatial multiplexing using a single transmissionlayer Mode 7 DCI format 1A Common and If the number of PBCH antennaports is UE specific by C-RNTI one, Single-antenna port, port 0 is used,otherwise Transmit diversity DCI format 1 UE specific by C-RNTISingle-antenna port, port 5 Mode 8 DCI format 1A Common and If thenumber of PBCH antenna ports is UE specific by C-RNTI one,Single-antenna port, port 0 is used, otherwise Transmit diversity DCIformat 2B UE specific by C-RNTI Dual layer transmission, port 7 and 8 orsingle-antenna port, port 7 or 8 Mode 9 DCI format 1A Common andNon-MBSFN subframe: If the number of UE specific by C-RNTI PBCH antennaports is one, Single- antenna port, port 0 is used, otherwise Transmitdiversity MBSFN subframe: Single-antenna port, port 7 DCI format 2C UEspecific by C-RNTI Up to 8 layer transmission, ports 7-14 orsingle-antenna port, port 7 or 8 Mode 10 DCI format 1A Common andNon-MBSFN subframe: If the number of UE specific by C-RNTI PBCH antennaports is one, Single- antenna port, port 0 is used, otherwise Transmitdiversity MBSFN subframe: Single-antenna port, port 7 DCI format 2D UEspecific by C-RNTI Up to 8 layer transmission, ports 7-14

TABLE 6 Transmission Control channel Search Transmission scheme of PDSCHmode DCI format Space corresponding to PDCCH Mode 1 DCI format 1A Commonand Single-antenna port, port 0 UE specific by C-RNTI DCI format 1 UEspecific by C-RNTI Single-antenna port, port 0 Mode 2 DCI format 1ACommon and Transmit diversity UE specific by C-RNTI DCI format 1 UEspecific by C-RNTI Transmit diversity Mode 3 DCI format 1A Common andTransmit diversity UE specific by C-RNTI DCI format 2A UE specific byC-RNTI Transmit diversity Mode 4 DCI format 1A Common and Transmitdiversity UE specific by C-RNTI DCI format 2 UE specific by C-RNTITransmit diversity Mode 5 DCI format 1A Common and Transmit diversity UEspecific by C-RNTI Mode 6 DCI format 1A Common and Transmit diversity UEspecific by C-RNTI Mode 7 DCI format 1A Common and Single-antenna port,port 5 UE specific by C-RNTI DCI format 1 UE specific by C-RNTISingle-antenna port, port 5 Mode 8 DCI format 1A Common andSingle-antenna port, port 7 UE specific by C-RNTI DCI format 2B UEspecific by C-RNTI Single-antenna port, port 7 or 8 Mode 9 DCI format 1ACommon and Single-antenna port, port 7 UE specific by C-RNTI DCI format2C UE specific by C-RNTI Single-antenna port, port 7 or 8 Mode 10 DCIformat 1A Common and Single-antenna port, port 7 UE specific by C-RNTIDCI format 2D UE specific by C-RNTI Single-antenna port, port 7 or 8

TABLE 7 Control channel Search DCI format Space Transmission scheme ofPDSCH corresponding to PDCCH DCI format 1A Common and UE specific If thenumber of PBCH antenna port is one, Single-antenna by Temporary C-RNTIport, port 0 is used, otherwise Transmit diversity DCI format 1 UEspecific by If the number of PBCH antenna port is one, Single-antennaTemporary C-RNTI port, port 0 is used, otherwise Transmit diversity

In order to increase a peak data rate, it is necessary to transmit manydata in unit time. TO this end, it is necessary to support a bigtransport block size. As a size of a transport block (TB) is gettingbigger, the number of code blocks constructing a transport block mayincrease as well. In this case, when an error occurs on a partial codeblock only among the entire code blocks, if the entire transport blocksare retransmitted, it may lead to system performance deterioration.Hence, when a single transport block includes a plurality of codeblocks, the present invention proposes a method of performingretransmission in a unit of a code block. If the present invention isapplied, it is able to enhance throughput performance of a wirelesscommunication system.

Assume that a transport block exceeding a specific size is segmentedinto a plurality of code blocks. A CRC (cyclic redundancy check) can beattached to a transport block to detect an error and a CRC can beattached to each of a plurality of code blocks to detect an error. Inthis case, a length of the CRC attached to the transport block may bedifferent from a length of the CRC attached to the code block. Inparticular, it is preferable to generate the CRSs from generatorpolynomials different from each other.

In order to perform retransmission in a unit of a code block, it ispreferable to detect a code block at which an error occurs via a CRC byperforming decoding on the entire code blocks included in a transportblock. And, it is preferable to transmit information on the code blockat which the error occurs to a transmitting side (or transmitting end).Having received the feedback information on the code block at which theerror occurs, the transmitting side retransmits the code block at whichthe error occurs only. In this case, it is preferable to transmitinformation on the retransmitted code block via a control channel toenable HARQ combining. A receiving side performs HARQ combining on theretransmitted code block with the previously transmitted code blocks andperforms decoding. The transmitting side performs retransmission on acode block at which an error occurs only until an error does not occuror until a retransmission count becomes a maximum retransmission countusing the same method.

Method of Providing Feedback on Code Block Error Information

If the number of code blocks constructing a transport block is equal toor less than a predefined number, a receiving side may provide feedbackon ACK/NACK in a unit of a single ACK/NACK bit for the entire transportblock rather than a unit of a code block. When the receiving endsuccessfully performs decoding on all code blocks due to theretransmission of a transmitting end, the receiving end may transmit ACKfor the transport block while not transmitting ACK/NACK for the codeblocks. When the transmitting side performs retransmission as many asthe maximum retransmission count, if the receiving end fails tosuccessfully perform decoding on all code blocks, the receiving end maytransmit NACK for the transport block while not transmitting ACK/NACKfor the code blocks.

Meanwhile, the receiving side can provide feedback on information on thecode blocks (e.g., code block index) to the transmitting side togetherwith ACK/NACK information on a plurality of the code blocks. The codeblock index can be defined in an order of concatenating the code blocks.Or, when the transmitting end segments the code blocks, the transmittingend can transmit index information to the receiving end by adding theinformation to the segmented code block. In this case, ACK/NACK of acode block at which an error occurs can be transmitted as follows. Whenthe receiving side transmits ACK/NACK in a unit of a code block, it ispreferable not to transmit ACK/NACK for a transport block configured bythe code block.

Method 1: A Receiving Side Defines an Order of Concatenating a Pluralityof Code Blocks by a Code Block Index, Concatenates ACK/NACK of Each CodeBlock and Transmits the Concatenated ACK/NACK to a Transmitting SideUsing a Bitmap Scheme.

According to a method 1-1 corresponding to a detail embodiment of themethod 1, a length of the bitmap can be determined by a maximum value ofthe number of code blocks. If the number of code blocks constructing ascheduled transport block is less than a maximum value of the number ofcode blocks, it is preferable for the receiving side to transmit NACK asACK/NACK for a code block excluding a code block in which ACK/NACK isactually detected by decoding. For example, assume that it is able toschedule a transport block consisting of maximum 100 code blocks. Inthis case, if a transport block consisting of 60 code blocks isscheduled, ACK/NACK corresponding to 60 bits is obtained for 60 codeblocks and NACK is transmitted for the remaining 40 code blocks.ACK/NACK information of code blocks expressed by a bitmap is channelencoded again and can be transmitted.

According to a method 1-2 corresponding to a detail embodiment of themethod 1, receiving side may transmit ACK/NACK for only scheduled codeblocks by a type of bitmap. In this case, receiving side may feedbackinformation on the number of scheduled code blocks. It may be preferableto independently encode the number of code blocks and ACK/NACKinformation.

According to a method 1-3 corresponding to a detail embodiment of themethod 1, if the number of code blocks at which an error occurs is equalto or greater than a specific value, a transmitting side may retransmitall transport blocks. To this end, it may use a bitmap value thatrepresents all code blocks as NACK. Or, it may designate and use aspecific bitmap value.

According to a method 1-4 corresponding to a specific embodiment of themethod 1, if the number of code blocks at which an error occurs is equalto or greater than a specific value, a transmitting side may retransmitall transport blocks. In this case, a receiving side may transmit singlebit ACK/NACK instead of a bitmap. This can be comprehended as thereceiving side transmits ACK/NACK for a transport block. The ACK/NACKfor the transport block may transmitted via a physical channel differentfrom a physical channel on which ACK/NACK for a code block istransmitted.

If the number of code blocks at which retransmission actually occurs isnot that big, ACK/NACK for the retransmission can be replaced with asingle ACK/NACK bit. In this case, the transmitted single ACK/NACK bitis ACK only when retransmitted code blocks are all successful.Otherwise, the single ACK/NACK bit is NACK. As a different method, itmay be able to generate and transmit a bitmap corresponding to thenumber of retransmitted code blocks. In this case, the bitmap can betransmitted in a manner of being mapped according to an order of a codeblock index used for the first transmission.

Method 2: Method of Transmitting an Index of a Code Block at Which anError Actually Occurs

The number of indexes varies according to the number of code blocks atwhich an error occurs. Hence, a transmitting side additionally transmitsinformation on the number of errors of code blocks to a receiving sideand the receiving side can eliminate ambiguity capable of being occurredwhen the receiving side performs decoding. It is preferable to encodethe information on the number of errors of code blocks and informationon a code block index, respectively. In this case, if the number of codeblocks at which an error occurs is equal to or greater than a specificvalue, the transmitting side may retransmit all transport block.

Method 3: Method of Generating Single ACK/NACK Per a Code Block GroupIncluding One or More Code Blocks Instead of a Transport Block to ReduceFeedback Overhead

A receiving side receives a transport block from a transmitting side.The transport block can include a plurality of code blocks. And, a codeblock group can include one or more code blocks. In this case, ACK/NACKmay be transmitted in a unit of a code block group in response to thereceived transport block. The code block group may include at least onecode block. ACK/NACK for a code block group including one or more codeblocks is transmitted as ACK only when an error does not occur afterdecoding is performed on all code blocks included in the code blockgroup. If an error occurs on any code block, it is preferable totransmit NACK. According to the method 1, a bitmap of an index of a codeblock group is transmitted. According to the method 2, an index of acode block group at which an error occurs is transmitted (it may includeinformation on the number of code block groups at which an error occursas well).

When a receiving side provides a feedback on ACK/NACK for a code block,a channel for transmitting the ACK/NACK can be defined. The receivingside can transmit ACK/NACK information for a code block for a downlink(DL) transport block via PUSCH (physical uplink shared channel). In thiscase, the PUSCH may apply channel coding (e.g., tail bitingconvolutional coding) different from channel coding (e.g., turbo coding)used for transmitting user data. The PUSCH carrying ACK/NACK for aplurality of code blocks may be transmitted via a time-frequencyresource predefined by a transmitting/receiving side without anindication indicated by a DL control channel. Or, the PUSCH carryingACK/NACK for a plurality of code blocks may be scheduled via a DLcontrol channel of a format different from a DL control channel thatschedules a general user data. When PUSCH on which ACK/NACK istransmitted and PUSCH on which user data is transmitted are transmittedat the same time in a single subframe, it may consider methods describedin the following.

-   -   It may put a priority on the PUSCH carrying ACK/NACK than PUSCH        carrying user data and the PUSCH carrying user data is not        transmitted. In case of using such a multiple access scheme as        SC-FDMA, it may have a merit in terms of PAPR.    -   It may transmit the PUSCH carrying ACK/NACK and the PUSCH        carrying user data at the same time. In case of using such a        multiple access scheme as OFDMA, it may have a merit in terms of        latency.    -   ACK/NACK-related information and user data information are        independently encoded while the PUSCH carrying ACK/NACK and the        PUSCH carrying user data are transmitted at the same time. This        is because ACK/NACK and user data require a different error        rate. In case of using such a multiple access scheme as SC-FDMA,        it may have a merit in terms of PAPR. However, since it is        necessary to transmit the user data by performing puncturing on        the user data, reception performance of the user data can be        deteriorated.

ACK/NACK information of a code block for a UL transport block istransmitted via PDSCH. In this case, the PDSCH may apply channel coding(e.g., tail biting convolutional coding) different from channel coding(e.g., turbo coding) used for transmitting user data. The PDSCH carryingACK/NACK for a plurality of code blocks can be transmitted via atime-frequency resource predefined by a transmitting/receiving sidewithout an indication indicated by a DL control channel Or, the ACK/NACKinformation of a code block for a UL transport block can be scheduledvia a DL control channel of a format different from a DL control channelthat schedules a general user data. When PDSCH on which ACK/NACK istransmitted for a specific user and PDSCH on which user data istransmitted are transmitted at the same time in a single subframe, itmay consider methods described in the following.

-   -   The PDSCH on which ACK/NACK is transmitted and the PDSCH on        which user data is transmitted can be transmitted via a        different frequency resource. In this case, the PDSCH on which        ACK/NACK is transmitted and the PDSCH on which user data is        transmitted may use a different channel coding scheme.    -   ACK/NACK can also be transmitted on the PDSCH on which user data        is transmitted. In this case, it is preferable to independently        encode the ACK/NACK and the user data. In this case, the        ACK/NACK and the user data may use the same channel coding        scheme.

In case of supporting retransmission in a unit of a code block, a DLcontrol channel (e.g., PDCCH/EPDCCH) used for retransmission by atransmitting side may include control information different from that ofa DL control channel for initial transmission. For example, DL controlinformation for initial transmission may include information on atransport block (e.g., information on a transport block size). On thecontrary, the DL control channel indicating retransmission may includeinformation on a code block to be retransmitted (e.g., the number ofcode blocks, a code block index, a code block group index, etc.) inaddition to the information on a transport block included in the DLcontrol information for the initial transmission. Or, the DL controlchannel indicating retransmission may include information on code blockto be retransmitted (e.g., the number of code blocks, a code blockindex, a code block group index, etc.) instead of the information (e.g.,information on a transport block size) on a transport block included inthe DL control information for initial transmission. This is because,when retransmission is performed, although a transport block size is notchanged, since a code block or a code block group at which an erroroccurs is retransmitted only, the transmitting side provides informationon code block to be retransmitted to the receiving side to make thereceiving side perform HARQ combining.

The aforementioned contents of the method 3 can be applied to the method1 and the method 2.

The above-described embodiments correspond to combinations of elementsand features of the present invention in prescribed forms. And, therespective elements or features may be considered as selective unlessthey are explicitly mentioned. Each of the elements or features can beimplemented in a form failing to be combined with other elements orfeatures. Moreover, it is able to implement an embodiment of the presentinvention by combining elements and/or features together in part. Asequence of operations explained for each embodiment of the presentinvention can be modified. Some configurations or features of oneembodiment can be included in another embodiment or can be substitutedfor corresponding configurations or features of another embodiment. And,it is apparently understandable that an embodiment is configured bycombining claims failing to have relation of explicit citation in theappended claims together or can be included as new claims by amendmentafter filing an application.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

A method of transmitting/receiving a HARQ ACK/NACK signal in a wirelesscommunication system can be applied to various wireless communicationsystems including 3GPP LTE/LTE-A, 5G system, and the like.

What is claimed is:
 1. A method for transmitting a hybrid automaticrepeat and request acknowledgement (HARQ-ACK) signal by a user equipmentin a wireless communication system, the method comprising: receiving atransport block (TB) containing a plurality of code blocks from a basestation, one or more code block groups (CBGs) being determined from theplurality of code blocks; based on a number of the one or more CBGsbeing less than a maximum number of CBGs for the TB, generating anegative-acknowledgement (NACK) value for each of at least one remainingCBG other than the one or more CBGs from among the maximum number ofCBGs for the TB; and transmitting the HARQ-ACK signal including the NACKvalue for each of the at least one remaining CBG to the base station. 2.The method of claim 1, wherein the transmitted HARQ-ACK signal includesan ACK value for a CBG when all code blocks of the CBG are successfullydecoded.
 3. The method of claim 1, wherein the transmitted HARQ-ACKsignal includes an NACK value for a CBG when any code block of the CBGis not successfully decoded.
 4. The method of claim 1, wherein one ACKvalue or NACK value is transmitted per CBG.
 5. The method of claim 1,further comprising: receiving, from the base station, a retransmissionof a CBG corresponding to an NACK value from among the one or more CBGs.6. A method for receiving a hybrid automatic repeat and requestacknowledgement (HARQ-ACK) signal by a base station in a wirelesscommunication system, the method comprising: transmitting a transportblock (TB) containing a plurality of code blocks to a user equipment,one or more code block groups (CBGs) being determined from the pluralityof code blocks; and based on a number of the one or more CBGs being lessthan a maximum number of CBGs for the TB, receiving, from the userequipment, the HARQ-ACK signal including a negative-acknowledgement(NACK) value for each of at least one remaining CBG other than the oneor more CBGs from among the maximum number of CBGs for the TB.
 7. Themethod of claim 6, wherein one ACK value or NACK value is received perCBG.
 8. The method of claim 6, further comprising: retransmitting, tothe user equipment, a CBG corresponding to an NACK value from among theone or more CBGs.
 9. A user equipment for transmitting a hybridautomatic repeat and request acknowledgement (HARQ-ACK) signal in awireless communication system, the user equipment comprising: a receiverconfigured to receive a transport block containing a plurality of codeblocks from a base station, one or more code block groups (CBGs) beingdetermined from the plurality of code blocks; a processor configured to,based on a number of the one or more CBGs being less than a maximumnumber of CBGs for the TB, generate a negative-acknowledgement (NACK)value for each of at least one remaining CBG other than the one or moreCBGs from among the maximum number of CBGs for the TB; and a transmitterconfigured to transmit the HARQ-ACK signal including the NACK value foreach of the at least one remaining CBG to the base station.
 10. The userequipment of claim 9, wherein the transmitted HARQ ACK signal includesan ACK value for a CBG when all code blocks of the CBG are successfullydecoded.
 11. The user equipment of claim 9, wherein the transmittedHARQ-ACK signal includes an NACK value for a CBG when any code block ofthe CBG is not successfully decoded.
 12. The user equipment of claim 9,wherein one ACK value or NACK value is transmitted per CBG.
 13. A basestation for receiving a hybrid automatic repeat and requestacknowledgement (HARQ-ACK) signal in a wireless communication system,the base station comprising: a transmitter configured to transmit atransport block (TB) containing a plurality of code blocks to a userequipment, one or more code block groups (CBGs) being determined fromthe plurality of code blocks; and a receiver configured to, based on anumber of the one or more CBGs being less than a maximum number of CBGsfor the TB, receive, from the user equipment, the HARQ-ACK signalincluding a negative-acknowledgement (NACK) value for each of at leastone remaining CBG other than the one or more CBGs from among the maximumnumber of CBGs for the TB.
 14. The base station of claim 13, wherein oneACK value or NACK value is received per CBG.
 15. The base station ofclaim 13, wherein the transmitter is further configured to retransmit,to the user equipment, a CBG corresponding to an NACK value from amongthe one or more CBGs.
 16. The user equipment of claim 9, wherein thereceiver is further configured to receive, from the base station, aretransmission of a CBG corresponding to an NACK value from among theone or more CBGs.